Brush assembly for rotary electrical apparatus



April 8, 1969 H. w. FLETCHER 3,437,975

BRUSH ASSEMBLY FOR ROTARY ELECTRICAL APPARATUS Filed April 11. 1966 v 35 A r 37 34 36 .Fia

- v INVENTOR.

lhmy W/ km/ER 4 7- roz/vsys United States Patent U.S. Cl. 3391 4 Claims ABSTRACT OF THE DISCLOSURE A brush assembly for a miniature rotary electrical component is disclosed. The brush is a wire which extends through a terminal in the component housing. The wire is held in physical and electrical contact with the terminal only by a cap member clamping means.

This invention relates generally to miniature rotary electrical apparatus which utilizes slip rings and brush assemblies to feed information generated by a movable electrical contact through the housing of such apparatus and more particularly to a brush assembly for use with such apparatus.

This specification and the drawing will be directed particularly to a potentiometer structure which utilizes a brush assembly in accordance with the present invention. Such is done for the purposes of ease of description and illustration and clarity of definition of the invention. It should, however, be expressly understood that the present invention is not to be limited to utilization with potentiometers but rather has a much broader scope of application and can be utilized with any rotary electrical apparatus to which the brush assembly might be adapted.

-In the prior art wherein brush assemblies particularly of a miniature nature have been utilized, it has been customary to manufacture the same out of a precious metal which for the most part is an alloy containing gold. These contact brushes have been inserted through an opening in the electrical terminal and then, after crimping the terminal to physically hold the brush, have been soldered in place to provide positive mechanical and electrical contact between the brush and the terminal which extends through the housing of the apparatus. It has been found that such soldering of the brush element to the terminal has resulted in deleterious efifect's to the brush. Such, it is throught, has occurred because of the solder permeating the pores of the precious met-a1 alloy. This permeation appears to embrittle the brush material and, when the same is placed under tension for any period of time such as is required for normal operation of a typical brush in contact with a slip ring in a rotary electrical apparatus, the brush breaks or bends sufficiently at its point of being soldered so that any tension or pressure which is required for good electrical contact with the slip ring is lost.

Utilizing such prior art techniques the brush had to be assembled with the terminal member prior to assembly of the remainder of the apparatus. Such was required because upon location of the brush in the terminal solder had to then be applied in order to maintain the brush in the desired position. As a result thereof, expensive assembly procedures necessarily had to be provided and followed. Furthermore, it should "be recognized that, particularly in miniature rotary electrical apparatus, the production worker is handling extremely small devices. For example, the terminal typically defines an opening on the order of 20 mils in diameter through which the brush is inserted while the brush wire itself is on the order of mils in diameter. Thus it can be seen that the apparatus embodying the brush assembly is very delicate, thus creating additional problems in attempting to place the solder in exactly the right position. It can therefore be seen that to utilize the prior art brush assembly techniques great expense is incurred.

Accordingly, it is an object of the present invention to provide an electrical brush assembly for utilization with rotary electrical apparatus, which brush assembly is simple, easy to install and yet performs the desired function without failure or breaking.

It is another object of the present invention to provide a brush assembly which is utilizable with electrical rotary apparatus and which is rugged and reliable under normal operating conditions.

It is a further object of the present invention to provide a brush assembly for utilization with rotary electrical apparatus which can be installed after the remainder of the electrical rotary apparatus has been fully assembled and tested.

It is yet a further object of the present invention to provide a brush assembly which is utilizable with rotary electrical apparatus and which brush assembly can be 'blindly installed into the fully assembled rotary electrical apparatus.

It is yet another object of the present invention to provide a brush assembly for utilization with rotary electrical apparatus which eliminates the necessity of any soldering, welding or similar type bonding techniques.

Additional objects and advantages of the present invention both as to its organization and method of operation will become apparent from a consideration of the following description taken in conjunction with the accompanying drawing which is presented by way of example only and is not intended as a limitation upon the scope of the present inventionas defined in the claims appended hereto and in which:

FIGURE 1 is a cross-sectional view of a rotary electrical apparatus embodying a brush assembly in accordance with the present invention;

FIGURE 2 is a side eleva-tional view partly in crosssection of a fully assembled brush assembly which may be utilized in a device similar to that illustrated in FIG- URE 1;

FIGURE 3 is a top, elevational view of the structure of FIGURE 2; and

FIGURE 4 is a cross-sectional view of the terminal utilized in a brush assembly in accordance with the present invention.

A brush assembly for utilization in a rotary electrical apparatus includes a terminal means which is affixed rigidly in the housing of the rotary electrical apparatus and which terminal means defines an opening therethrough. An electrically conductive wire means is placed in such a position as to extend through the opening in the terminal means and into the housing and into electrical contact with a rotary electrical element positioned within the apparatus. Clamping means then is placed into contact with the terminal means and the wire means in such a manner that the clamping menas secures the terminal and the wire means in good physical and electrical contact. The clamping means is the only such securing device used in the brush assembly.

Referring now to the drawing and more particularly to FIGURE 1 thereof, there is illustrated a potentiometer 10 having a housing 11 within which there is rotatably disposed a shaft 12. The shaft 12 carries a slip ring 13 and a slip ring 14. The slip ring is an electrically conductive member rigidly afiixed to the shaft 12 for rotation therewith. Also aflixed to the slip ring 13 is a contact member 15 which engages an electrical element such as a resistance element 16. Afiixed to the slip ring 14 is a contact 17 which engages an electrical resistance element 18. Thus as the shaft 12 is rotated, the contact elements 15 and 17 are caused to move over the surfaces of the resistance elements 16 and 18 respecitvely. This therefore varies, for example, the electrical resistance or voltage which would appear at the slip ring 13 and 14 respectively when compared to a fixed contact on the resistance element as is well known in the prior art.

A brush member in the form of an electrically conductive wire means 21 is in contact with the slip ring 13 and extends through a terminal 22 which is rigidly affixed to the housing 11 and mechanically supports the brush 21 in engagement with the slip ring 13. A similar brush 23 is in contact with the slip ring 14 and extends through a terminal 24 which is similar to the terminal 22. Not only do the terminals 22 and 24 support the brush members 21 and 23 as above deescribed, but also provide means by which an electrical contact may be made to other portions of an electrical circuit for utilization, again as is well known in the prior art.

Again it is to be emphasized that although a brush assembly in accordance with the present invention is illustrated in FIGURE 1 in utilization with a potentiometer, such is not intended to be a restriction upon the invention but merely an indication of one application thereof.

Referring now to FIGURE 2, the brush assembly separated from the utilizing apparatus is illustrated more in detail. As is therein shown, the terminal means includes an outer ring 31 having a lower section 32 provided with a plurality of serrations therea-bout as is illustrated. The lower section 32 is inserted into the opening in the housing and the serrations permit a gripping by the ring 31 to rigidly affix the terminal means in place on the housing. An upper rim 33 is also provided on the ring 31, the rim 33 being utilized to limit the distance by which the terminal means can be inserted into the housing. The terminal means also includes an inner electrically conductive tubular section 34 defining an axially extending opening 35 therethrough. An insulating means 36 is disposed between the tube 34 and the ring 31 to electrically isolate the tube 34 from the housing 11. Typically, the tube 34, the ring 31 and the insulating medium 36- are insert molded to provide an integral unit as illustrated in the drawing. For purposes of orientation, the terminal member such as illustrated particularly in FIGURE 4 would have typical dimensions of .156 inch in diameter and .227 inch in length and would define the opening therethrough on the order of .020 inch in diameter.

At the upper end of the tube 34 there is provided a head portion 37. As is illustrated particularly in FIGURE 3, one side of the head 37 is removed to provide a flat surface 38. An electrically conductive brush such as wire means 41 is inserted through the opening 35. One end of the wire means 41 defines a bight 42 which is adapted to receive that portion of the flange 37 which defines the flattened surface 38 as is clearly illustrated in FIGURE 2. A cap member 43 fits over and surrounds the flange 37 and the bight 42 in the wire means 41. The lower peripheral edge 44 of the cap 43 is crimped and simultaneously therewith the end 45 of the wire 41 is also crimped. In this manner the wire 41 is mechanically rigidly aflixed to the terminal means and forms excellent electrical contact therewith. It can therefore be seen that good electrical contact is formed but there is no physical fusing or bonding as is normally the case when soldering or welding occurs. For example, if the cap 43 were to be removed from a completed brush assembly, the wire mem- 4 ber 41 could readily be removed therefrom by merely straightening the end 45 thereof.

In assemblying the structure as illustrated in the drawing particularly at FIGURES 2, 3 and 4, the bight 42 is first placed in the wire 41 providing a sufficient distance between the two legs of the bight so that the flattened portion of the flange 37 can be received therebetween. The wire 41 is then inserted through the opening 35 in such a manner that the bight 42 is in place as is illustrated in FIGURES 2 and 3. The cap is then placed over the flange 37 and the bight 42 and at this point is crimped in place. Thereafter, the brush assembly is inserted into the opening in the housing in such a manner that the wire means 41 contacts the slip ring as illustrated in FIG- URE 1.

There has thus been disclosed a brush means for utilization with rotary electrical apparatus which is extremely simple and easy of assembly and installation and which provides strong mechanical and electrical bonding without the utilization of Welding, soldering or other similar bonding techniques.

What is claimed is:

1. In a miniature electrical apparatus having a housing and a rotary electrical element, a brush contact assembly for establishing electrical contact through said housing with said rotary element comprising:

(a) terminal means adapted to be affixed rigidly in said housing and defining an opening thereth'rough;

(b) electrically conductive wire means extending through said opening, into said housing, and into electrical contact with said rotary electrical element; and

(c) cap member clamping means contacting said terminal means and said wire means and covering said opening in said terminal means,

(1) said clamping means being the only securing device for maintaining sald terminal and wire means in good physical and electrical contact.

2. A brush contact assembly as defined in claim 1 wherein said wire means defines at one end thereof a bight, said bight receiving said terminal means and said clamping means encompassing said bight.

3. A brush contact assembly as defined in claim 2 wherein said terminal means defines an electrically conductive portion having an end area and a flat surface area on one side thereof, one portion of said wire means defining said bight being in engagement with said flat surface area.

4. A brush contact assembly as defined in claim 3 wherein said clamping means is a cap member having a peripheral edge and covering said flat surface area, said peripheral edge being inwardly turned thereby to firmly maintain said wire in electrical contact with said flat surface area.

References Cited UNITED STATES PATENTS 2,904,767 9/ 1959 Vacha. 2,991,379 7/1961 Van Dam 3l0239 3,267,412 8/1966 Rosenberg et al. 339276 FOREIGN PATENTS 338,882 6/1959 Switzerland.

RICHARD E. MOORE, Primary Examiner.

US. Cl. X.R. 339276 

